1. Field of the Invention
The present invention relates to locomotive parking brakes and, more specifically, to an electromechanical motorized locomotive parking brake with brake chain tension control.
2. Description of the Related Art
Locomotive parking brakes are used to set and hold the locomotive brakes in the applied position so that a locomotive remains parked when unattended. Due to the weight of a locomotive, the parking brake must be able to apply a large amount of force. As manual parking brakes require a user to either apply a significant force or operate a hand mechanism over a long period of time, there are numerous motorized versions that reduce the amount of manual labor involved. Due to need for both manual and motorized inputs, conventional locomotive parking brakes are usually designed so that use of the motorized function will not cause the manual mechanism to operate. For example, U.S. Pat. No. 1,491,753 discloses the use of a central gear or gears that may be selectively driven by either a motor or a hand wheel. Because the central gears are coupled to both the motor and the hand wheel via corresponding worm gears, operation of either the motor or the hand wheel will not cause the other input to be correspondingly operated through the common linkage as the two inputs are disengaged from each other. Other approaches avoid this consequence by disengaging the inputs from each other using a clutch than mechanically disconnects one of the inputs from the gears.
One problem associated with the use of a motorized locomotive parking brake is the need for feedback of how much force is being applied to the braking system by the motor. For example, the locomotive may be free to roll away in an uncontrolled fashion if the locomotive is parked on a grade an insufficient tension has been placed on the braking system. Correspondingly, if the motor applies too much tension the braking system may be damaged. The current approaches to solving this problem involve adding a load cell that continuously monitors brake chain tension or monitoring the input current to the motor as it is being operated. These approaches have drawbacks, however, as load cells are expensive and the motor current is not always an accurate gauge for the amount of force applied to the braking system. Accordingly, there is a need in the art for a motorized locomotive parking system that can provide the appropriate tension to the braking system.